Leptospirosis in the Asia Pacific region

<p>Abstract</p> <p>Background</p> <p>Leptospirosis is a worldwide zoonotic infection that has been recognized for decades, but the problem of the disease has not been fully addressed, particularly in resource-poor, developing countries, where the major burden of the disease occurs. This paper presents an overview of the current situation of leptospirosis in the region. It describes the current trends in the epidemiology of leptospirosis, the existing surveillance systems, and presents the existing prevention and control programs in the Asia Pacific region.</p> <p>Methods</p> <p>Data on leptospirosis in each member country were sought from official national organizations, international public health organizations, online articles and the scientific literature. Papers were reviewed and relevant data were extracted.</p> <p>Results</p> <p>Leptospirosis is highly prevalent in the Asia Pacific region. Infections in developed countries arise mainly from occupational exposure, travel to endemic areas, recreational activities, or importation of domestic and wild animals, whereas outbreaks in developing countries are most frequently related to normal daily activities, over-crowding, poor sanitation and climatic conditions.</p> <p>Conclusion</p> <p>In the Asia Pacific region, predominantly in developing countries, leptospirosis is largely a water-borne disease. Unless interventions to minimize exposure are aggressively implemented, the current global climate change will further aggravate the extent of the disease problem. Although trends indicate successful control of leptospirosis in some areas, there is no clear evidence that the disease has decreased in the last decade. The efficiency of surveillance systems and data collection varies significantly among the countries and areas within the region, leading to incomplete information in some instances. Thus, an accurate reflection of the true burden of the disease remains unknown.</p

Emergence of new leptospiral serovars in American Samoa - ascertainment or ecological change?

Background: Leptospirosis has recently been discussed as an emerging infectious disease in many contexts, including changes in environmental drivers of disease transmission and the emergence of serovars. In this paper, we report the epidemiology of leptospiral serovars from our study of human leptospirosis in American Samoa in 2010, present evidence of recent serovar emergence, and discuss the potential epidemiological and ecological implications of our findings.Methods: Serovar epidemiology from our leptospirosis seroprevalence study in 2010 was compared to findings from a study in 2004. The variation in geographic distribution of the three most common serovars was explored by mapping sero-positive participants to their place of residence using geographic information systems. The relationship between serovar distribution and ecological zones was examined using geo-referenced data on vegetation type and population distribution.Results: Human leptospirosis seroprevalence in American Samoa was 15.5% in 2010, with serological evidence that infection was caused by three predominant serovars (Hebdomadis, LT 751, and LT 1163). These serovars differed from those identified in an earlier study in 2004, and were not previously known to occur in American Samoa. In 2010, serovars also differed in geographic distribution, with variations in seroprevalence between islands and different ecological zones within the main island.Conclusions: Our findings might indicate artefactual emergence (where serovars were long established but previously undetected), but we believe the evidence is more in favour of true emergence (a result of ecological change). Possibilities include changes in interactions between humans and the environment; introduction of serovars through transport of animals; evolution in distribution and/or abundance of animal reservoirs; and environmental changes that favour transmission of particular serovars.Future research should explore the impact of ecological change on leptospirosis transmission dynamics and serovar emergence, and investigate how such new knowledge might better target environmental monitoring for disease control at a public health level

Ultraviolet Light Inactivation of Murine Norovirus and Human Norovirus GII: PCR May Overestimate the Persistence of Noroviruses Even When Combined with Pre-PCR Treatments

Transmission of gastroenteritis-causing noroviruses may be significant via contaminated surfaces. Measures for control, e.g. disinfection with ultraviolet irradiation (UV), are therefore necessary for interrupting this transmission. Human norovirus (HuNoV) GII.4 and Murine norovirus (MuNoV) were used to study the efficacy of UV for virus inactivation on dry glass surfaces. MuNoV inactivation was measured using viability assay and the reduction in viral RNA levels for both viruses using reverse transcription quantitative PCR (RT-QPCR). For each UV dose, two parallel sample groups were detected using RT-QPCR: one group was enzymatically pre-PCR treated with Pronase and RNAse enzymes, while the other was not treated enzymatically. In the viability assay, loss of infectivity and a 4-log reduction of MuNoV were observed when the viruses on glass slides were treated with a UV dose of 60 mJ/cm2 or higher. In the RT-QPCR assay, a steady 2-log decline of MuNoV and HuNoV RNA levels was observed when UV doses were raised from 0 to 150 mJ/cm2. A distinct difference in RNA levels of pretreated and non-pretreated samples was observed with UV doses of 450–1.8 × 103 mJ/cm2: the RNA levels of untreated samples remained over 1.0 × 10³ PCR units (pcr-u), while the RNA levels of enzyme-treated samples declined below 100 pcr-u. However, the data show a prominent difference between the persistence of MuNoV observed with the infectivity assay and that of viral RNA detected using RT-QPCR. Methods based on genome detection may overestimate norovirus persistence even when samples are pretreated before genome detection